1. Field of the Invention
The present invention relates to a structure of a flying type head slider used in a disk drive.
2. Description of the Related Art
In recent years, a reduction in size and an increase in capacity of a magnetic disk drive as a kind of external storage device for a computer have been desired. One method of increasing the capacity of the magnetic disk drive is to increase the number of magnetic disks mounted on a spindle, and in association therewith the spacing between the magnetic disks in a recent magnetic disk drive has increasingly been reduced. Further, a flying type head slider becomes to be used to apply a bias magnetic field in a magneto-optic disk drive. Particularly in a recent magnetic disk drive, a flying type magnetic head adopting a contact start and stop (CSS) system has been frequently used.
In such a flying type magnetic head adopting the CSS system, a magnetic head comes to contact with a magnetic disk when the disk drive stops operation, whereas the magnetic head is kept flying at a microscopic height from the disk surface by an air flow generating over the disk surface rotating at a high speed in recording or reproducing information.
In the flying type magnetic head adopting the CSS system, an electromagnetic transducer (magnetic head element) is built in a slider for receiving the air flow generating over the disk surface, and the slider is supported by a suspension. Accordingly, when the magnetic disk remains still, the slider including the electromagnetic transducer is in contact with the disk surface, whereas when the magnetic disk is rotated, a disk opposing surface of the slider opposed to the magnetic disk receives an air flow generated by rotation of the magnetic disk, and the slider flies from the disk surface. The electromagnetic transducer built in the slider is moved over the disk surface as being supported by the suspension to perform recording or reproduction of information at a given track.
In a magnetic disk drive employing a conventional flying type magnetic head slider, a pair of rails are provided on opposite side portions of a disk opposing surface of the magnetic head slider opposed to the disk surface. Each rail has a flat air bearing surface. Further, a tapering surface is formed on each rail so as to meet an air inlet end surface of the slider. The air bearing surface of each rail receives an air flow generated by high-speed rotation of a magnetic disk to fly the slider and stably maintains a microscopic distance between the disk surface and the electromagnetic transducer.
According to the CSS system, a high flying stability and a microscopic flying height (submicrons) can be ensured. However, when the disk remains still, rail surfaces (air bearing surfaces) of the slider are in contact with the disk. Accordingly, when the magnetic disk drive starts or stops operation, the air bearing surfaces relatively slide on the disk. To cope with such sliding, a protective film made of a hard material such as carbon and a lubricating layer for reducing friction and wear of the protective film to improve durability of the magnetic disk are formed on a recording layer of the disk. Owing to the presence of the lubricating layer, friction and wear of the protective film can be reduced; however, when the disk drive stops operation, there is a possibility that stiction between the disk and the slider may occur to cause a problem that the disk drive cannot be restarted.
In association with a recent increase in amount of information, the development in high density, large capacity, and small size of a magnetic disk drive has become remarkable, and the occurrence of stiction has been greatly highlighted as a cause of faulty operation due to a reduction in torque of a spindle motor in association with the size reduction and due to smoothing of the disk surface for the high density. To reduce the stiction between the slider and the disk, it has been proposed to perform crowning of the flying surfaces (rail surfaces) of the slider over the entire length in the longitudinal direction to thereby reduce a contact area between the slider and the disk.
While the slider thus crowned is effective for prevention of the stiction, there is a problem that variations in working accuracy are large and an increase in cost of the slider is invited, so that such a slider is unsuitable for mass production. Further, crowning is performed in the longitudinal direction of each flying surface of the slider, so that each rail surface of the slider becomes nearer to the disk than the electromagnetic transducer (head element) formed on an air inlet end surface of the slider, causing a problem that a spacing loss is produced.
Further, the use of a contact type head intended to attain a zero flying height has recently started to be considered in response to the development in high density, and it is therefore more important to prevent the stiction between the disk and the slider causing faulty operation and fracture of the electromagnetic transducer or the recording layer of the disk. To prevent this stiction problem, it has been proposed to provide a plurality of projections (pads) on the flying surfaces (air bearing surfaces) of the slider, thereby reducing a contact area between the slider and the disk surface (Japanese Patent Laid-open No. 8-69674).
The magnetic head slider described in this publication is characterized in that the plural pads are formed on the rails to avoid the direct contact between the rail surfaces (air bearing surfaces) of the slider and the magnetic disk surface. However, the conventional magnetic head slider with the pads has a problem such that when the magnetic disk drive is stopped and thereafter restarted, a frictional force and a sticking force between the slider and the magnetic disk surface are greatly increased in some case. This problem is considered to be due to the fact that the pads formed on the rails have scraped the lubricant present on the magnetic disk surface.
Such scraping of the lubricant by the pads may be suppressed by thinning each pad to reduce the sectional area thereof. However, each pad must have a sufficient sectional area to some degree because each pad wears at stopping and restarting the magnetic disk drive. Further, a decrease in contact area between each pad and the disk surface causes remarkable wearing of each pad and an increase in contact pressure between each pad and the magnetic disk. As a result, there is a possibility that the lubricant layer formed on the disk surface may be broken or the disk surface may be worn.